Control of contrast with aromatic diamine color developers



Nov. 16, 1948. F. w. H. MUELLER 2,454,001

7 CONTROL OF CONTRAST WITH AROMATIC DIAMINE COLOR DEVELOPERS Filed NOV.8, 1945 COL-0R POSFHVE FlLM R 7. t V} Z m D LOG ExPosuRE' 3.0 COLORNEGATIVE. Fn..M

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LOG EXPOSURE M INVENTOR FRITZ W.H. MUELLER 8Y3 Q M ATToR NEY PatentedNov. 16, 1948 CONTROL OF CONTRAST WITH ,AROMATIC DIAMIN E COLORDEVELOPERS Fritz W. H. Mueller, Binghamton,

N. Y., assignor to General Aniline & Film Corporation, New York, N. Y.,a corporation of Delaware Application November 8, 1945, Serial No.627,329

4 Claims.

This invention relates to color photography, and more particularly to adevelopment of color images by means of aromatic diamine developingagents in the presence of protein decomposition products in order tocontrol the contrast of color images obtained upon coupler development.

In color photography, it is well-known that dye images are formed by acoupling reaction of an oxidized primary aromatic amine developing agentwith a suitable organic compound having an active methylene or reactiveethenol group. As development proceeds, the corresponding azomethine orindophenol dyes are formed in situ with the silver image. Speed andgradation control are readily accomplished in the usual dye couplingprocess, but difficulties are encountered in controlling the contrast orgamma of the color image to obtain the proper color balance. Colordevelopers which are-used in subtractive color processes are Well-knownin the prior art, and comprise reducing agents which, when acting uponexposed silver-halide, produce oxidation products which in turn yieldinsoluble dye images with suitable color couplers. Such color couplersmay be either incorporated as non-difiusing color components in theindividual layers of a, multicolor subtractive process or may be addedto the color developer in difiusible form.

It is known that natural proteins of very high molecular weight andprotein decomposition products of medium to high molecular weight withinthe range of the molecular weights of lysalbinic acid, gelatose and thelike, have been added to ordinary black and white developers, 1. e.,developers containing mono-amines alone, or in combination Withhydroquinone or other adjuvants in order to yield softer silver imagesof finer grain. Developing agents of the monoamine type, whether aloneor in combination with other adjuvants and in the presence of proteindecomposition products as described in United States Patent 2,164,687,do not control the contrast or gamma of the color images produced inmulti-color subtractive processes. In other words, fine grain developersdo not exert a selective influence on the gamma of the characteristiccurve representing the dependence of developed color density upon thelogarithm of exposure in the individual layer of the multi-layersubtractive color film.

I have discovered that the addition of a relatively small quantity of aprotein decomposition product of medium to high molecular weight, asdescribed in U. S. 2,164,687 to color developers of the aromatic diaminetype gives an improvement in color balance 'of the dye image byselective adjustment of the gradation of the characteristic curves ofthe magenta and even more of the cyan layer. This discovery is ofspecial value in subtractive multi-layer film where the various layersare developed simultaneously by a, single color developer solution. Itappears that the rate of penetration of the color developer, and therate of coupling of the color coupler varies, and that the color balanceis not distorted if the gamma of the characteristic curves in the threeindividual layers is approximately the same. In other words, if one ofthe layers shows an excessive contrast, the color balance is inferiorand color falsification results in the final picture.

The photographic multi-layer materials, which may be processed with thedevelopers of the present invention, are color-reversible film,colornegative film, color-positive film, color-reversible printingmaterial coated on a white opaque film base or color-positive printingmaterial coated on paper. A color-reversible film, as prepared accordingto United States Patent 2,186,849, consists of an integral tripackemulsion coated on the usual clear cellulose acetate or nitrate filmbase. Each of the three emulsion layers contains a color-former and issensitized to one of the primary colors of light. The top layer isblue-sensitive and contains a color-former for the yellow dye image. Afilter layer, yellow in color and blue absorbing, lies underneath thetop layer. Below this filter layer lies the green-sensitive emulsionlayer containing a color-former for the magenta dye image. The bottomlayer is a redsensitive emulsion layer containing a color-former for thecyan dye image. The color-negative film is made up in the same manner asthe colorreversible film, with the exception that it may contain a layerof clear gelatin between the redsensitive layer and the green-sensitivelayer. The color-reversible opaque materia1 is prepared in the samemanner as the color-reversible film, with the exception that the baseconsists of an opaque white film. The color paper is made up in the samemanner as the color-reversible film, with the exception that theemulsions are coated on a baryta-coated paper base. When thesilver-halide latent image is developed with a primary aromatic aminodeveloper, the oxidation product of the developing agent reacts-with thecolor-formers to give a colored dye image.

As examples of suitable aromatic diamine developing agents which may beemployed with the protein decomposition products, there may be mentionedp-phen'ylenediamine, p-aminoethylanor primary amino group in the phenylnucleus which enables the oxidation product of the developer to couplewith the color-former to form a dye image in the emulsion adjacent tothe individual particles of the silver image. The silver image may beremoved by bleaching in the well-known manner to leave the color imagein the emulsion- A suitable developing solution is prepared as follows:

p-Diethylamino aniline hydrochloride "grams" 2.5 Sodium sulfite(anhydrous) do 1.0 Sodium carbonate (monohydrate) do 67.5 Potassiumbromide do 2.0 Water to make liter 1 The concentration of proteindecomposition products such as sodium lysalbinate, peptone, gelatose andsimilarprotein degradation products may range from to grams per liter ofdeveloper solution. A concentration approaching grams per liter has thetendency of not only reducing the contrast of the cyan image, but maylead to stain and reduction of the maximum density of the dye image. Theoptimum concentration resulting in optimal color balance can be readilyascertained for the various types of color film and papers and for thevarious species of diamine developing agents by a few routineexperiments.

The present invention is illustrated by the ac companying drawing inwhich Figures 1 to 2represent typical characteristic curves of the colordensities in the individual layers obtained on color positive and colornegative films as described be,-

low by way of examples and the films treated in the manner set forth.

In Figures 1 to 2, wherein the ordinates represent densities and theabscissa represent the log of exposure, A, B, and C (which representyellow, magenta and cyan, respectively) are the density curves for colorpositive and color negative films, respectively, which have been exposedand developed in an aromatic diamine developing agent in the ordinarymanner, and A, B, and C, are the density curves for the same type offilm exposed under the same conditions and 'treated with a diaminedeveloping agent in the presence of a protein decomposition product inaccordance with the present invention.

The following examples will serve to specifically describe the inventionas applied to color positive and color negative films. These examplesshould not be construed as limiting or' restricting the presentinvention, but should be considered merely as illustrative.

Example I minutes in a color developer as above described.

Th n t ur a an? 9 a ll strated in Figure 1, were obtained by reading thecolor densities in the individual yellow, magenta and cyan layers, byemploying the proper filters in a photoelectric densitometer in a knownmanner. From this figure, it will be observed that the cyan layer, C,has too steep a gradation to obtain a good color balance.

By adding 5 grams of sodium lysalbinate to a liter of the same colordeveloper and developing a similarly exposed color positive film, thecontrast of the cyan layer, C, was noticeably reduced as shown by thedotted line C, whereas the curves A (yellow) and B (magenta) werealtered very slightly as shown by dotted lines A and B, respectively.

Example II A multi-color subtractive negative film was developed with acolor developer as hereinbefore described without the presence of aprotein decomposition product. The density curves obtained were plottedas A, B, and C shown in Figure 2,. From these curves, it will beobserved that their shape is quite irregular and substantially altered,

By adding 5 grams of sodium lysalbinate to a liter of the same colordeveloper and developing a similarly exposed color negative film, theshape of these curves, A, B, and C, are more uniform, particularly inthe high densities, as shown by the dotted lines A, B, and C.

Example III Similar results as obtained in Examples I and II wereprocured when peptone and gelatose were substituted for sodiumlysalbinate in equal amounts.

While I have herein disclosed the preferred embodiments of my invention,I do not desire to limit myself solely to the specific examples, sinceit will be readily apparent to those skilled in the art that preciseratios of protein decomposition products and the aromatic diaminedeveloping agent may be varied and other materials having equivalentchemical or physical properties may be employed without departing fromthe spirit and scope thereof. As for example, instead of employing theprotein decomposition products specifically disclosed herein,polypeptides either synthetically prepared or obtained by controlledprotein hydrolysis in the known manner may be employed with satisfactoryresults. Accordingly, therefore, only such limitations should be imposedas are indicated in the appended claims.

I claim:

1. The process of preventing the formation of excessively contrasty dyeimages in the individual layers of a multi-layer color film containingsilver-halide emulsions and color formers which comprises exposing thefilm and developing simultaneously all layers with a solution of anaromatic diamine developing agent containing a primary amino group and 5to 15 grams per liter of said solution of a protein decomposi tionproduct of medium to high molecular weight substantially within therange of the molecular weights of lysalbinic acid and gelatose, themolecules of thesaid protein decomposition products being built up of atleast five amino acids.

2. The process of preventing the formation of execssively contrasty dyeimages in the individual layers of a multi-layer color film containingsilver-halide emulsions and color'formers which comprises exposing thefilm and developing simultaneously all layers with a solution of an.sweetie d st ld elqnin e t c lil e a primary amino group and 5 to 15grams per liter of said solution of sodium lysalbinate.

3. The process of preventing the formation or excessively contrasty dyeimages in the individual layers of a multi-layer color film containingsilver-halide emulsions and color formers which comprises exposing thefilm and developing simultaneously all layers with a solution of anaromatic diamine developing agent containing a primary amino gI'OllP and5 to 15 grams per liter of said solution of gelatose.

4. The process of preventing the formation of excessively contrasty dyeimages in the individual layers of a multi-layer color film containingsilver-halide emulsions and color formers which comprises exposing thefilm and developing simultaneously all layers with a solution of anaromatic diamine developing agent containing a primary amino group and 5to 15 grams per liter of said solution of peptone.

FRITZ W. H. MUELLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Henney, Handbook of Photography,Mc- Graw-Hill Book Company, Inc., 1939, pages 335 and 337 cited.

Riegel, Industrial Chemistry, Reinhold Publishing Corporation, 1937,page 620 cited.

